2 ms·

Ok, so lets go with your use case. You can run basic java ("hello world") under 3MB with a startup time of about 0.1 second. So that is the true overhead if you

by npalli 13y ago

Ok, so lets go with your use case. You can run basic java ("hello world") under 3MB with a startup time of about 0.1 second. So that is the true overhead if you really care about tight code. The default values are pretty large. Everything else (memory/startup) is added due to external libraries that are needed and additional memory as the program grows. Given that "kkowalczyk" talked about 10K line programs, what applications are you thinking of that are 10K lines and cannot tolerate a 0.1 second/3 MB overhead. Would you restart java everytime? Note that even a simple helloworld c program has about 0.01second/0.5MB overhead.

m0th87 13y ago
I was going to say there's no way java programs boot in 0.1 seconds, but looked it up to be sure. Here's the results on my mac/i7, defaulted to server mode: $ time java HelloWorld Hello, world! real 0m0.101s Touche. 0.1 seconds is exactly right, at least on my setup. That said, javac is slow given the program is 5 lines of code: $ time javac HelloWorld.java real 0m0.511s user 0m0.833s sys 0m0.050s And I'd ventured to guess that there must be something to the JIT being pretty slow for real-world applications, otherwise people wouldn't complain so frequently about it. Maybe aspects of JIT optimizations increase linearly-ish with the amount/complexity of code? FWIW, we went with go at my work instead of java because our application is memory-intensive, and there's huge gains there in go over java.
- bchjam 13y ago
  A program that consists solely of println("Hello, World!"); is pretty stateless and trivial, there's not much that a JIT could do with this. Somewhat anecdotally, I remember hearing Rich Hickey talking about how the JVM JIT loves stateless code. I'm pretty sure the vast majority of Java code in use is deeply stateful. I don't know how much of a difference this actually makes but it seemed like a relevant data point.
tptacek 13y ago
You are off by two orders of magnitude in the C case, at least with my trivial test case of writing hello world, and then a runner program that forks/execs/waitpids 10,000 times. If you know what crt0.c does, you can see C is also pretty much the asymptote of what you're going to get from program startup, so it's a little silly to make the comparison.
eliasmacpherson 13y ago
Is that with the JVM already running or not?

by npalli 13y ago

m0th87 13y ago

I was going to say there's no way java programs boot in 0.1 seconds, but looked it up to be sure. Here's the results on my mac/i7, defaulted to server mode: $ time java HelloWorld Hello, world! real 0m0.101s Touche. 0.1 seconds is exactly right, at least on my setup. That said, javac is slow given the program is 5 lines of code: $ time javac HelloWorld.java real 0m0.511s user 0m0.833s sys 0m0.050s And I'd ventured to guess that there must be something to the JIT being pretty slow for real-world applications, otherwise people wouldn't complain so frequently about it. Maybe aspects of JIT optimizations increase linearly-ish with the amount/complexity of code? FWIW, we went with go at my work instead of java because our application is memory-intensive, and there's huge gains there in go over java.

bchjam 13y ago
A program that consists solely of println("Hello, World!"); is pretty stateless and trivial, there's not much that a JIT could do with this. Somewhat anecdotally, I remember hearing Rich Hickey talking about how the JVM JIT loves stateless code. I'm pretty sure the vast majority of Java code in use is deeply stateful. I don't know how much of a difference this actually makes but it seemed like a relevant data point.

tptacek 13y ago

You are off by two orders of magnitude in the C case, at least with my trivial test case of writing hello world, and then a runner program that forks/execs/waitpids 10,000 times. If you know what crt0.c does, you can see C is also pretty much the asymptote of what you're going to get from program startup, so it's a little silly to make the comparison.

eliasmacpherson 13y ago

Is that with the JVM already running or not?